Viscosity of liquids containing spherical molecules or ions

The temperature dependence of the viscosity of some molecular and ionic liquids is examined. Liquids composed of spherical molecules or ions obey the Arrhenius viscosity equation throughout the liquid range, while liquids containing non-spherical molecules or ions deviate from Arrhenius behaviour. This supports previous conclusions that, in the Arrhenius region, a molecule must be free to rotate many times during the time between translational jumps.